Very low noise RF nMOSFETs on plastic by substrate thinning and wafer transfer

A very low minimum noise figure (NF/sub min/) of 1.2 dB and a high associated gain of 12.8 dB at 10 GHz were measured for six-finger, 0.18-/spl mu/m radio frequency (RF) metal-oxide semiconductor field-effect transistors mounted on insulating plastic following substrate-thinning (/spl sim/30 /spl mu/m) and wafer transfer. Before this process, the devices had a slightly better RF performance of 1.1-dB NF/sub min/ and a 13.7-dB associated gain. The small RF performance degradation of the active transistors transferred to plastic shows the potential of integrating electronics onto plastic.     

Far field radiation from an arbitrarily oriented Hertzian dipole in the presence of a layered anisotropic medium

Far field radiation from an arbitrarily oriented Hertzian dipole for two-layered uniaxially anisotropic medium with a tilted optic axis is treated analytically by using the dyadic Green's function of the problem when the dipole is placed over or embedded in a two-layered uniaxially anisotropic medium. The radiation fields are evaluated using the steepest descent method. Parameter studies including anisotropy, layer thickness and dipole location are performed to investigate the effects of changing different variables on the radiation fields. Results of this work can be applied in microstrip circuits and antennas.     

Low-loss LTCC cavity filters using system-on-package technology at 60 GHz

In this paper, three-dimensional (3-D) integrated cavity resonators and filters consisting of via walls are demonstrated as a system-on-package compact solution for RF front-end modules at 60 GHz using low-temperature cofired ceramic (LTCC) technology. Slot excitation with a /spl lambda/g/4 open stub has been applied and evaluated in terms of experimental performance and fabrication accuracy and simplicity. The strongly coupled cavity resonator provides an insertion loss <0.84 dB, a return loss >20.6 dB over the passband (/spl sim/0.89 GHz), and a 3-dB bandwidth of approximately 1.5% (/spl sim/0.89 GHz), as well as a simple fabrication of the feeding structure (since it does not require to drill vias to implement the feeding structure). The design has been utilized to develop a 3-D low-loss three-pole bandpass filter for 60-GHz wireless local area network narrow-band (/spl sim/1 GHz) applications. This is the first demonstration entirely authenticated by measurement data for 60-GHz 3-D LTCC cavity filters. This filter exhibits an insertion loss of 2.14 dB at the center frequency of 58.7 GHz, a rejection >16.4 dB over the passband, and a 3-dB bandwidth approximately 1.38% (/spl sim/0.9 GHz).     

Probing stress effects in HfO2 gate stacks with time dependent measurements

Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO₂ dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (V_t) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on V_t.     

Dielectric reliability of stacked Al2O3–HfO2 MIS capacitors with cylinder type for improving DRAM data retention characteristics

Dielectric reliability in Al₂O₃(2–3.1nm)–HfO₂(3nm) stack capacitor with Metal–Insulator–Si(MIS) structure is investigated in this paper. We propose an optimized capacitor process through the Time–Dependent Dielectric Breakdown (TDDB) data under various process conditions. Furthermore, due to asymmetric current at both negative and positive voltage stress polarities, we show different lifetime extrapolation by a fluence–driven model. As a result, the maximum allowed operating voltage is projected to be 1.7V (failure rate 10ppm during 10year @ 85°C) for Data “0” retention lifetime.     

Structural Fault Based Specification Reduction for Testing Analog Circuits

Specification reduction can reduce test time, consequently, test cost. In this paper, a methodology to reduce specifications during specification testing for analog circuit is proposed and demonstrated. It starts with first deriving relationships between specifications and parameter variations of the circuit-under-test (CUT) and then reduces specifications by considering bounds of parameter variations. A statistical approach by taking into account of circuit fabrication process fluctuation is also employed and the result shows that the specification reduction depends on the testing confidence. A continuous-time state-variable benchmark filter circuit is applied with this methodology to demonstrate the effectiveness of the approach.     

Magnetic effects of direct ion implantation of Mn and Fe into p-GaN

In p-GaN implanted with Mn (3×10¹⁶ cm⁻² at 250 keV), the material after annealing shows ferromagnetic properties below 250 K. Cross-sectional transmission electron microscopy (TEM) revealed the presence of platelet structures with hexagonal symmetry. These regions are most likely Ga_xMn_1−xN, which produce the ferromagnetic contribution to the magnetization. In p-GaN implanted with Fe, the material after annealing showed ferromagnetic properties at temperatures that were dependent on the Fe dose, but were below 200 K in all cases. In these samples, TEM and diffraction analysis did not reveal any secondary phase formation. The results for the Fe implantation are similar to those reported for Fe doping during epitaxial growth of GaN.     

Electrical and growth characteristics of Au/Al0.15Ga0.85N:Si structures with various Si incorporations

We have investigated the growth characteristics of n-Al_0.15Ga_0.85N:Si/GaN and the electronic properties of Au/n-Al_0.15Ga_0.85N:Si diode structures grown by metal-organic chemical vapor deposition (MOCVD) with various Si incorporations. The Al_0.15Ga_0.85N:Si layers were grown on undoped GaN/sapphire (0001) epitaxial layers in a horizontal MOCVD reactor at the reduced pressure of 300 torr. The mirrorlike surface, free of defects, such as cracks or hillocks, can be seen in the undoped Al_0.15Ga_0.85N epilayer, which was grown without any intentional flow of SiH₄. However, many cracks are observed in the n-Al_0.15Ga_0.85N:Si, which was grown with Si incorporation above 1.0 nmol/min. While Au/n-Al_0.15Ga_0.85N:Si diodes having low incorporation of Si showed retively good rectifying behavior, the samples having high Si incorporation exhibited leaky current-voltage (I-V) behavior. Particularly, the Au/n-Al_0.15Ga_0.85N:Si structure grown with Si incorporation above 1.0 nmol/min cannot be used for electrical rectification. Both added tunneling components and thermionic emission influence the current transport at the Au/n-Al_0.15Ga_0.85N:Si barrier when Si incorporation becomes higher.     

Magnetism in SiC implanted with high doses of Fe and Mn

High concentrations (0.1–5 at.%) of Mn or Fe were introduced into the near-surface region (≤2000 Å) of 6H-SiC substrates by direct implantation at ～300°C. After annealing at temperatures up to 1000°C, the structural properties were examined by transmission electron microscopy (TEM) and selected-area diffraction pattern (SADP) analysis. The magnetic properties were examined by SQUID magnetometry. While the Mn-implanted samples were paramagnetic over the entire dose range investigated, the Fe-implanted material displayed a ferromagnetic contribution present at <175 K for the highest dose conditions. No secondary phases were detected, at least not to the sensitivity of TEM or SADP.     

On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks

An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.